package day08.FanXing;

import java.util.ArrayList;

public class Lian04 {
    public static void main(String[] args) {
        fun1(new ArrayList<Animal>());
        fun2(new ArrayList<BlackDog>());
        fun3(new ArrayList<Animal>());
    }
    public static void fun1(ArrayList<?>list){}
    public static void fun2(ArrayList<?extends Dog>list){}
    public static void fun3(ArrayList<?super Dog>list){}

}
class Animal{

}
class Dog extends Animal{

}
class BlackDog extends Dog{

}